Vibration meter system for vibratory compaction machines

ABSTRACT

A soil and road-grade compaction machine includes a heavy rigid frame, a roller having a power driven eccentric weight rotating about the roller axis, and cushion means which allows the roller to vibrate with only nominal movement of the frame. The vertical component of the movement of the roller relative to the frame or &#39;&#39;&#39;&#39;bounce&#39;&#39;&#39;&#39; of the roller operates an electric current generator having its output inductively attenuated and then rectified and measured by a meter which indicates any increase or decrease in the bounce of the roller in relative terms.

KR. ante-17? United State Baker et Dec. 11, 1973 VIBRATION METER SYSTEM FOR VIBRATORY COMPACTION MACHINES [75] Inventors: Edwin J. Halter, Elm Grove;

Norman L. Peterson, Wauwatosa, both of Wis.

[73] Assignee: Rex Chainbelt Inc., Milwaukee, Wis.

[22] Filed: Dec. 30, 1971 [21] Appl. No.: 214,290

[51] Int. Cl. E01c 19/38 [58] Field of Search 404/117, 84, 133;

[56] References Cited UNITED STATES PATENTS 3,053,157 9/1962 Martin 404/117 3,153,993 10/1964 Keppler 404/117 3,283,679 11/1966- Rafferty..... 404/117 3,610,029 10/1971 Carlson 73/7l.4

3,391,571 7/1968 Johanson 73/7l.5

FOREIGN PATENTS OR APPLICATIONS 673,215 6/1966 Belgium.. 404/117 509,086 l/l955 Italy 335/276 Primary ExaminerRamon S. Britts Assistant ExaminerThomas J. Holko AtzomeyErnst W. Schultz et al.

[5 7] ABSTRACT A soil and road-grade compaction machine includes a heavy rigid frame, a roller having a power driven eccentric weight rotating about the roller axis, and cushion means which allows the roller to vibrate with only nominal movement of the frame. The vertical component of the movement of the roller relative to the frame or bounce of the roller operates an electric current generator having its output inductively attenuated and then rectified and measured by a meter which indicates any increase or decrease in the bounce of the roller in relative terms.

8 Claims, 5 Drawing Figures PATENTED DEC] 1 I973 sum 1 m g PATENTEI] DEC] 1 I975 smear? Ill VIBRATION METER SYSTEM FOR VIBRATORY COMPACTION MACHINES BACKGROUND OF THE INVENTION The field of the invention is essentially soil compaction in preparation for the making of roadways.

The prior art includes vibratory rollers of the type which are adapted to move at relatively high speeds over the grade under preparation. As distinguished from rollers which are merely weighted to effect compaction, these rollers are vibrated vertically to effet compaction. However, their effectiveness requires that they vibrate at or near the frequency of ground resonance which changes as the machine traverses different types of soil or fill or with each successive pass over the same soil or fill. Prior art devices carried by the machine frame to indicate vibration amplitude of the frame are not effective with compaction machines of recent development having greatly increased frame weight and mass and improved isolation such that the frame, the engine and the operators platform vibrate very little.

The prior art includes devices which indicate amount of vibration but does not include reliable devices capable of indicating amplitude of vibration as such and which will survive the millions of cycles of vibration required generally in the frequency range of 300 to 1,800 cycles per minute or to 30 cycles per second.

SUMMARY OF THE INVENTION The output of a field-supplied alternating current generator having an oscillating armature is connected by an inductive reactance through rectifiers to a galvanometer which indicates the amplitude of armature oscillation generally independently of oscillation frequency at least within the range of its application. The generator stator is carried by the relatively nonvibrating frame of a soil compaction machine and the generator armature is driven by a vertical link connected to the vibrating element of the machine. The meter indicates directly any increase or decrease in the amplitude of vertical vibration of the element, which change may be due to achange in ground resonance or the operators change of vibration frequency toward or away from the frequency of ground resonance. Such indications thus allow the operator at any time to quickly find or confirm the vibration frequency which provides maximum effective compaction while the machine is in operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation of a vibratory compaction machine with some parts shown with broken lines;

FIG. 2 is an enlarged section taken on line 2-2 of FIG. 1 and through the axis of the roller;

FIG. 3 is a side elevation of the generator and includes a part of the frame and a part of the vibrating element to which the generator stator and armature are connected;

FIG. 4 is a section taken on line 4-4 of FIG. 3; and

FIG. 5 is a diagram of the windings of the generator and of the input and output circuits.

DESCRIPTION OF THE PREFERRED EMBODIMENT The self-propelled vibratory roller shown in the drawings includes the articulated frames 11 and 12 which are connected by the pin 13 for relative pivotal steering movement about a central vertical axis. The rubber tired wheels M support frame If which carries the engine 15 and the operators control station 16.

The rectangular frame l2 surrounds the compaction roll 20 and is of U-shaped section. A shown in FIG. 2, the end discs 22 of roll 20 are provided with hubs 23 each having inner and outer bearings 24 and 25, re spectively. Bearings 25 support the hubs 26a and 26b of the two cushion members 28 which support frame 12. For that purpose, each side member 29a and 29b of frame 12 is provided with a circular housing 12a in which the respect cushion member is securely pressed. The shaft 30 carrying the eccentric weights 31 within roll 20 are rotatably supported by bearings 24. One end of shaft 30 is connected to the output shaft of the hydraulic motor 32 which is fixed to hub 26b. The other end of shaft 30 is connected to a drive line which connects the shaft and a tachometer, not shown, provided at the control station 16. The terminal housing 33 of the drive line referred to is secured to hub 26a.

An hydraulic system, not shown, includes a pump driven by engine 15, and a motor, not shown, which drives wheels 14. A hydraulic cylinder, not shown, connects the two frames 11 and I2 and is controlled by the operator to effect steering of the machine. Other conventional controls, not shown, allow the operator to control the speed and direction or travel of the machine and the speed of rotation of shaft 30 by motor 32.

A preferred form of the generator 41, as shown, may be provided by modifying a conventional transformer which includes primary and secondary windings on the center leg of a laminated core. Such a core is modified to comprise a stator 42 of an E section and an armature 43 in the form of an I section and which are separated by an arcuate air gap which has a geometric center in the central plane of the core and parallel to the crosspiece of the E section. The bracket M which supports the stator 42 is located within and secured by bolts 45 to the side member 29a of frame 112.

The stator 42 is clamped between the arms d7 of bracket 44 so that it is rigidly fixed with respect to frame 12. The armature 43 is clamped between the flanged members 48 which are bolted to the movable end of the lever 49. Lever 49 comprises a rigid, lightweight casting and is of an inverted U-shaped configuration.

In operation, roller l0 traverses the ground or prepared soil or fill whatever number of times may be needed to compact the soil to the depth and density required. For that purpose, motor 32 rotates shaft 30 at a speed selected by the operator which appears to provide maximum compaction. The isolation of the roll 20 from frame 12 allows the roll to move eccentrically and the vertical component provides the main compactive effort. Thus, under any given condition, maximum amplitude is considered to indicate the maximum compaction which can be accomplished. On soft ground, the maximum amplitude of the roll can be observed within a broad range which is very often entirely adequate. Obviously, it is desireable to be able to reach the required compaction with as few passes as required. However, and especially where the compaction requirement is difficult to achieve, on the second and subsequent passes, the optimum or critical speed of eccentric rotation is difficult to observe or detect by any means.

The present invention provides a well defined indication of relative changes in the amplitude of vertical vibration or bounce of the roll, even though the differences being compared are only small fractions of an inch.

The free end of lever 49 includes a flat plate 50. Members 48 are bolted to plate 50 with a number of intermediate shims 51 as may be required. The opposite end of lever 49 is provided with projecting trunnions 52 which are supported in the bearings 53 carried by the bracket 44. The axis of bearings 53 coincide with the geometric center of the arcuate air gap referred to and the shims 51 allow for adjustment of the air gap to a minimum practical width in the order of 0.006 and 0.010 inches.

The connecting link 55 comprises upper and lower ball and socket type rod ends 56 and 57, the threaded connecting member 58 and suitable lock nuts, as shown. The lower rod end 57 fits between two spaced lugs of lever 49. The lug 59 and the other lug which is broken away as shown in FIG. 3 carry the removable pin 60 which extends through the lower rod end 57. The upper rod end 56 fits between the two spaced lugs of the bracket 61 which is fixed by the bolts 62 to the hub 26a of one of the cushion members 28. The lug 63 and the other lug which is broken away, carry the removable pin 64 which extends through rod end 56.

The mechanical operation of generator 41 is effected by the connection of armature 43 with hub 26a through link 55 which is vertically disposed so that the vertical component of roll movement or bounce oscillates armature 43 about the axis of bearings 53 as will be described hereinafter.

Stator 42 includes two windings and as has been mentioned, they comprise the field and output windings 71 and 72, respectively, as shown in FIG. 5. The field winding 71 is connected in series with the source of D.C. voltage 73, the switch 74 and the potentiometer 75. The D.C. voltage source may, of course, be that provided for engine and switch 74 may be the ignition switch or a separate switch. Potentiometer 74 generally requires a single adjustment to place the output of generator 41 within the range of the D.C. meter 77.

Meter 77 may be a simple moving-coil (DArsonval) device with a single needle indicator or lamps, not shown, and is located at control station 16. The diodes 78 are arranged to rectify the alternating current of the output winding 72 of the generator 41. However, the value of inductance 79 which is connected in series with winding 72 is critical and is selected to attenuate the generator so that the voltage and current to meter 77 is reduced proportionate to any given increase in the frequency of the drive output of the generator. Additionally, of course, inductance 79 presents a high impedance to the small miscellaneous motions transmitted by link 55 to armature 43. In the operation of generator 41, each armature cycle reduces and restores the flux path across the air gap which in turn reduces and restores the magnetic field of winding 71 and generates a current in winding 72. For that purpose, the width of the cores of armature 43 and of stator 42 should be approximately equal to the maximum bounce" of roll considering further the length of the third class lever 49. Also, link 55 should be adjusted in length by turning the threaded rod 58 so that the excursion of the armature is approximately symmetrical respecting the stator.

While the voltage across field winding 71 may be from 6 to 12 volts in a typical embodiment of the invention, the output current of winding 72 is a fraction of a volt because of the unavoidable large loss of magnetic flux due to the air gap and the low operating frequency. The turns ratio of windings 71 and 72 may be in the order of 1:10 so that considering also that the field current is larger than the output current, the generator 41 as such might be considered a variable alternator.

The rotational speed of shaft 30 is typically between five and 30 revolutions per second and accordingly in a typical embodiment of the invention, the value of inductance 79 should be in the order of 25 Henrys and have a current capacity in the order of 300 ma. While both the distance and speed of armature motion determine the amount of current generated, the effect of inductance 79 at meter 77 provides the operator of roller 10 with a direct, visual indication of the bounce" of roll 20 and the compaction effectiveness at the particular speed, relative to that of another speed. This allows the operator to quickly find or preestablish the optimum speed of shaft 30 at any time. Similarly, any significant lower indication of meter 77 provides the operator with notice of a change in conditions wich suggest a needed change of shaft speed.

We claim:

1. In combination with a compaction machine having a frame of substantial mass, a ground engaging compaction element, resilient means interconnecting the frame and element, said element having manually controllable power-operated means effecting its vertical vibration at any selected frequency within a given range; current indicator means observable by the machine operator, an electric generator having an output winding, a stator fixed to and carried by said frame and an armature having a link connecting the same and said compaction element, said link being vertical such that the armature is oscillated by and in direct relation to the vertical movement of the compaction element relative to the frame, means for mounting and positively guiding the link so that movement of the armature carried by the link maintains a uniform air gap relative to the stator, and an inductive reactance connecting in series the output winding of said generator and said current indicator means whereby the current indicator means is operative to indicate relative changes in the amplitude of vertical movement of the element generally independently of the frequency of oscillation of the armature within said frequency range and whereby the machine operator by variously changing the vibration frequency of the element may readily find the frequency of ground resonance as indicated by a pronounced increase in current generation.

2. The combination of claim 1 wherein the current indicating means comprises a DArsonval meter with an indicator needle.

3. The combination of claim 1 wherein the compaction element is a roller and the power operated means effecting its vibration is a rotatable shaft concentric with the roller and having an eccentric weight.

4. The combination of claim 1 which further includes a source of direct current and wherein the stator includes a field winding connected to said source of direct current.

lever which is pivotally connected to the machine frame and to which the armature is fixed and the link is connected.

8. The combination of claim 7 wherein the armature oscillates along an arc and the effective length of the link is adjustable so that the excursion of the armature respecting the stator may be adjusted to be approximately equal in both directions. 

1. In combination with a compaction machine having a frame of substantial mass, a ground engaging compaction element, resilient means interconnecting the frame and element, said element having manually controllable power-operated means effecting its vertical vibration at any selected frequency within a given range; current indicator means observable by the machine operator, an electric generator having an output winding, a stator fixed to and carried by said frame and an armature having a link connecting the same and said compaction element, said link being vertical such that the armature is oscillated by and in direct relation to the vertical movement of the compaction element relative to the frame, means for mounting and positively guiding the link so that movement of the armature carried by the link maintains a uniform air gap relative to the stator, and an inductive reactance connecting in series the output winding of said generator and said current indicator means whereby the current indicator means is operative to indicate relative changes in the amplitude of vertical movement of the element generally independently of the frequency of oscillation of the armature within said frequency range and whereby the machine operator by variously changing the vibration frequency of the element may readily ''''find'''' the frequency of ground resonance as indicated by a pronounced increase in current generation.
 2. The combination of claim 1 wherein the current indicating means comprises a D''Arsonval meter with an indicator needle.
 3. The combination of claim 1 wherein the compaction element is a roller and the power operated means effecting its vibration is a rotatable shaft concentric with the roller and having an eccentric weight.
 4. The combination of claim 1 which further includes a source of direct current and wherein the stator includes a field winding connected to said source of direct current.
 5. The combination of claim 4 wherein the generator includes a laminated core of two parts separated by an air gap in the order of 0.006 to 0.010 inch, the stator and the two windings comprising one part and the armature comprising the other part.
 6. The combination of claim 4 wherein the turns ratio of the field and output windings are in the order of 1:10.
 7. The combination of claim 1 which the means for mounting and positively guiding the link includes a lever which is pivotally connected to the machine frame and to which the armature is fixed and the link is connected.
 8. The combination of claim 7 wherein the armature oscillates along an arc and the effective length of the link is adjustable so that the excursion of the armature respecting the stator may be adjusted to be approximately equal in both directions. 